Method of manufacturing a reaction vessel suitable for oxidation and decomposition processing with supercritical water

ABSTRACT

Disclosed is a reaction vessel used for oxidizing and decomposing equipment suitable for processing with supercritical water, and methods of manufacturing the reaction vessel. The reaction vessel comprises an oxide film containing a platinum group metal oxide for example having a fine crystalline structure, and a high corrosion resistance in both oxidizing and reducing atmosphere. The film is formed on a surface of the vessel by performing a pyrolysis reaction in an atmosphere containing water vapor. The oxide film is comprised of at least one platinum group metal oxide selected from Ir, Ru or Rh oxide, and at least one oxide of a metal selected from Ti and Ta.

This is a division of application Ser. No. 09/742,668, filed Dec. 20,2000 now U.S. Pat. No. 6,551,719. Each of these prior applications ishereby incorporated herein by reference, in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a reaction vessel for the use of oxidizationand decomposition processing equipment by supercritical water and amethod of manufacturing the reaction vessel in which harmful substancessuch as polybiphenyl chloride (hereinafter called as PBC), powerfultoxic dioxine and other organic compounds are processed to be theirnon-toxic states through oxidization and decomposition undersupercritical water condition with its critical temperature being 374°C. or higher and its critical pressure being 22 MPa or higher.

2. Description of the Related Art

In recent years, a chemical processing has been carried out frequentlyunder a supercritical state. For example, coffee and the like are mainlyused in extraction of food or separation of chemical products and thelike under a supercritical CO₂ where the processing is carried out undera relatively low temperature.

In the case of supercritical water, although its original substance iswater, there have been provided many cases that the supercritical wateris used in a normal chemical reaction and oxidization such as treatmentof environmental-relating materials such as decomposition of PCB,dioxine and the like due to the fact that its critical temperature isquite high, for example, the critical temperature is 374° C. or higherand the critical pressure is 22 MPa or higher.

These treatments are mainly carried out such that the materials aredissolved with water under supercritical state as solvent, then they arereacted with oxygen and decomposed. That is, since the supercriticalwater is liquid and at the same time it has also a characteristic actingas gas, where reaction with oxygen as gas must be almost freely carriedout.

That is, since the supercritical water is liquid and at the same timereaction with oxygen as gas can be carried out almost freely, theaforesaid materials can be quite easily dissolved due to the fact thatthe supercritical water becomes water of low molecules and dispersedwater which is different from the usual water, resulting in that thematerials and oxygen can be almost freely merged and reacted to eachother under such a processing condition as above and so its oxidizationand decomposition can be easily carried out.

SUMMARY OF THE INVENTION

However, in the case of the reaction vessel where such a strong reactionis performed, it occurred frequently the materials is generally exposedto the quite strong oxidizing atmosphere and at the same time in thecase of decomposition of harmful substances such as dioxine and thelike, the substances are completely decomposed, and resulting that Clcomponent becomes hydrochloric acid which show strong acid and theresulting liquid gives a strong corrosive characteristic and thereaction vessel itself is corroded.

Then, in the case of the prior art, reaction vessel used in theoxidization and decomposition treatment equipment of supercritical waterperforming such a reaction as above, Ni-based alloy material is normallyused, although it is not possible to say that this Ni-based alloymaterial has a sufficient anti-corrosive characteristic in its chemicalstability against acid-corrosion and therefore either replacement workcaused by the acid-corrosion or maintenance work such as a repairingoperation must be performed within a short period of time, which mustgive a problem to require high running cost and the improvement has beenhighly requested.

In view of the foregoing, as a countermeasure for the resolution againstthese problems, it has been tried that the inner surface of the reactionvessel is covered by anti-corrosive substances such as by Pt plating orthe like. But Pt is expensive, and not only a sufficient anti-corrosiveperformance could not be obtained, but also there occurred a problem ofa peeling-off of the Pt plated film and the like caused by a differenceof thermal expansion coefficient in respect to the reaction vessel(Ni-based alloy) accompanied by rapid increasing or rapid decreasing intemperature. In addition, although the Pt is durable against the acidatmosphere, the Pt shows a problem of crystal growth and peeling-off ordestruction of it in reducing atmosphere, so that actually it can not beapplied in such a objectives.

In view of such a circumstance as found in the prior art, the presentinventor made a various investigation to the subject matter and reachedthe present invention, wherein the objectives of the present inventionis to enable the reaction vessel to be covered and to be protectedagainst corrosive atmosphere in both oxidizing and reducing atmosphereand to provide a reaction vessel applicable in an oxidization anddecomposing processing equipment by supercritical water and a method ofmanufacturing the reaction vessel in which its durability is remarkablyimproved and its continuous use can be performed for a long period oftime.

In order to solve the problem, the present invention provides a reactionvessel applied in an oxidizing and decomposing processing equipment bysupercritical water, wherein an oxide film containing metal oxide havinga quite high anti-corrosive characteristic in both oxidizing andreducing atmosphere is formed at an inner surface of the vessel mainbody and the vessel is covered with the oxide film and protected by it.In this case, as the type of the reaction vessel structure, that is, anyof a vertical cylindrical vessel type or a coil type can be applied.

In addition, the present invention provides the aforesaid reactionvessel in which the oxide film contains platinum group metal oxidescomposed of fine crystalline structure showing a quite highanti-corrosive characteristic in both oxidizing and reducing atmosphere.

In addition, the present invention provides a reaction vessel in whichan oxide film contains at least one platinum group metal oxide selectedfrom Ir, Ru, and Rh.

In addition, the present invention provides a reaction vessel in whichan oxide film is comprised of a composite oxides containing platinumgroup metals and at least one metal selected from Ti, Ta.

In addition, the present invention provides a reaction vessel in whichan oxide film is comprised of a composite oxide containing Ir, and atleast one kind selected from Ti, and Ta by 20 to 50 at %, or a compositeoxides containing Ru, and at least one kind selected from Ti, and Ta by30 to 70 at %.

In addition, the present invention provides a method of manufacturing areaction vessel used in equipment for oxidizing and decomposingoperations with supercritical water, comprising the steps of: (1)applying a salt solution containing platinum group metals to the innersurface of the vessels main body to form a coating covering the surface:(2) pyrolyzing the coating in an atmosphere containing aqueous moistureto form a uniform, anti-corrosive, fine crystalline oxide film coveringthe surface.

In addition, the present invention provides a method of manufacturingthe aforesaid reaction vessel, wherein after performing a pretreatmentin which the surface of the vessel main body is degreased, its surfaceis processed with heat and said surface is formed with an oxide layer inadvance, the coating solution is applied to coat it.

In addition, the present invention provides a method of manufacturing areaction vessel, wherein an oxide film is comprised of a composite oxidecontaining Ir, at least one kind selected from Ti, and Ta by 20 to 50 at% or a composite oxide containing Ru, at least one kind selected fromTi, and Ta by 30 to 70 at %.

In addition, the present invention provides a method of manufacturing areaction vessel, wherein salt solution contains platinum group metalchloride, or alkoxide compound of platinum group metals.

Thus, in accordance with the aforesaid technical means, the reactionvessel showing the largest wear in the equipment for oxidizing anddecomposing processing with supercritical water is covered and protectedby an oxide film formed at the surface of the reaction vessel containingmetallic compound having a quite high anti-corrosive characteristic inboth oxidizing and reducing atmosphere, for example, an oxide filmcontaining platinum group metal oxide composed of fine crystals, therebythe reaction vessel is exposed in both oxidizing and reducing atmosphereat high temperature and high pressure for a long period of time and itsacid-based corrosion caused by reactant is restricted even under asevere environment such as heating and rapid cooling states. With suchan arrangement as above, it becomes possible to make a rapid progress ofanti-corrosive characteristic and durability of the reaction vessel anda substantial improvement of its practical application. In other words,it becomes possible to make a substantial reduction of running costaccompanied by either replacement or repairing of the reaction vesseland make a substantial improvement in its practical application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation showing one example of a preferredembodiment of the reaction vessel of the present invention (FIG. 1A)with a part being shown by a cross section view (FIG. 1B); and

FIG. 2 is an enlarged view showing a substantial part of anotherpreferred embodiment of the reaction vessel of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A preferred embodiment of the present invention is described as follows.

The vessel main body 1 is made of Ni-based alloy normally applied in theart, forms a well-known structure showing a vertical cylindrical vesseltype or a coil-type form (the vessel type is shown in the figure),wherein an oxide film containing metal oxide composed of crystallinestructure having a quite high anti-corrosive characteristic in bothoxidizing and reducing atmosphere, for example, an oxide film 2containing platinum group metal oxide is formed at an inner surface ofthe vessel main body by performing a pyrolysis decomposing reaction inatmosphere containing water vapor (refer to the enlarged view of FIG.1). In this way, the inner surface of the vessel main body 1 is coveredand protected by the oxide film 2, its anti-corrosive characteristicagainst acid becomes quite high even in the case that the reactionproduct shows a strong acid characteristic, resulting in that itsdurability makes a remarkable progress.

Although not shown, in the case that the vessel main body is of a vesseltype, it is of course apparent to say that it contains surrounding pipesor the like in addition to the vessel itself.

In the present invention, when the oxide film 2 formed at the innersurface of the vessel main body 1 is comprised of Ir—Ta based compositeoxides as indicated in Table 1, it is important in view of accomplishingthe present invention that an amount of content of Ta is restricted in arange of 20 to 50 at %.

A reason why this setting range is applied consists in the fact that ifthe amount of content of Ta is 20 at % or less, it becomes a uniformrutile type oxide under pyrolysis reaction, although a relative largecrack may easily be produced at a layer of the oxide film 2, and if theamount of content of Ta exceeds 50 at %, amorphous or crystallineseparated phase of oxide tantalum in addition to stable rutile oxide isproduced, though depending on a manufacturing condition of the reactionvessel, resulting in that the crack may easily be produced at the layerof the oxide film 2.

As described above, in the case that the oxide film 2 composed of Ir—Tabased composite oxides is formed at the inner surface of the vessel mainbody 1 by a pyrolysis process, it becomes important to restrict theamount of content of Ta within a range of 20 to 50 at %.

In the present invention, when the oxide film 2 formed at the innersurface of the vessel main body 1 is comprised of Ru—Ti based compositeoxides as indicated in Table 2, it is important in view of accomplishingthe present invention that an amount of content of Ti is restricted in arange of 30 to 70 at %.

A reason why this setting range is applied consists in the fact that ifthe amount of content of Ti is 30 at % or less, although the pyrolysisreaction may produce a uniform rutile-type oxide having titanium oxidesolid soluted with ruthenium oxide, not apparent, a relative large crackmay easily be produced at a layer of the oxide film 2, and if the amountof content of Ti exceeds 70 at %, anatase phase is produced in additionto rutile phase and the layer of the oxide film 2 is not made uniform.

As described above, in the case that the oxide film 2 composed of Ru—Tibased composite oxides is formed at the inner surface of the vessel mainbody 1 by a pyrolysis process, it becomes important to restrict theamount of content of Ti within a range of 30 to 70 at %.

Next, a method of manufacturing the vessel main body 1, i.e. a preferredmanufacturing method of forming the oxide film 2 on the inner surface ofthe vessel main body is described The Ni-based alloy of the vessel mainbody is activated, thereafter a salt solution containing platinum groupmetals is uniformly coated on the inside surface of of the vessel mainbody. The coating is then subjected to pyrolysis in an atmospherecontaining water vapor.

Although the surface treatment of the vessel main body 1 is notspecifically limited, it is preferable to avoid the rough surfaceformation at the surface and it is desirable to apply a degreasingprocess and an oxide forming process with surface heating process. Areason why these processes are applied consists in the fact that thepreforming of the oxide layer 3 improves an anti-corrosiveness of thevessel main body 1 itself and further its bonding with the oxide film 2can be increased more. Then, although the formation of the oxide layer 3to the inner surface of the vessel main body 1 is not specificallylimited, it can be carried out by a heat treatment of the vessel mainbody 1 in the air atmosphere. This processing can be carried out withits temperature during this process being in a range of about 500 to700° C. and further it can be performed in a range of about 600 to 900°C. in the water vapor atmosphere, where saturated with water vapor. Withthis arrangement above, it is possible to produce oxide layer 3 of quitedense and having a high adhering characteristic at the inner surface ofthe vessel main body 1.

In this way, the oxide film 2 containing platinum group metal compoundis formed at the inner surface of the vessel main body 1 formed withoxide layer 3 after performing a pre-treatment (refer to FIG. 2).

As platinum group metals forming the oxide film 2, it is desirable toapply at least one kind selected from Ir, Ru, and Rh having a superioranti-corrosive characteristic or these composite oxides and further toapply a composite oxides containing at least one kind selected from Ti,and Ta as stabilizing agent.

Then, the oxide film 2 can be obtained by applying coating solutioncomposed of aqueous solution containing salt or salt solution such asalcoholic solution and the like to the inner surface of the vessel mainbody 1 and drying it, thereafter a pyrolysis reaction processing withforced heating is performed with a temperature ranging from 350 to 700°C. in oxidizing atmosphere.

In this case, as salt solution, although it is possible to applyplatinum group metal chloride, or alkoxide compound of platinum groupmetals, it is preferable to avoid use of chloride that is apt to make adirect corrosion of the vessel main body 1 acting as the base material.

Further, in the case of using chloride, it is necessary to make anamount of content of chlorine minimum. That is, in the case that Irchloride acid, Ru chloride acid and/or Rh chloride are used as rawmaterial of platinum group metals, these chlorides are dissolved inadvance in alcohol such as amyl alcohol and the like, heated and drydistillated by a dry distillation equipment provided with a condenserand it is desirable to use material in which at least a part of Clcomponent is replaced with alcohol base. In this case, although this isdifferent in response to a processing time, the Cl component of 50 to70% is replaced with alcohol base through processing of 5 to 10 hours.

The salt processed in this way is dissolved in alcohol such as isopropylalcohol or butyl alcohol and the like or water to form coating solutionfor oxide film.

Then, it is desirable that as Ti or Ta, chloride is not used, but metalalkoxide such as butyl titanate or butyl tantalate and the like.

The coating solution for oxide film manufactured in this way is appliedto the inner surface of the vessel main body 1 acting as a basematerial, although its coating method is not restricted in particular,and it is important that the coating is applied as uniform as possiblewithout any irregular surface.

Normally, this is coated with a brush or spray coating and the like,thereafter the coated surface is naturally dried at a room temperature.Further, as required, a forced drying is carried out at a highertemperature of about 110° C. After drying it in this way, a pyrolysisreaction processing is carried out, although the oxide film 2 composedof fine crystalline structure having a quite high anti-corrosivecharacteristic can he formed at the inner surface of the vessel mainbody 1 in both oxidizing and reducing atmosphere by performing thepyrolysis reaction processing in the water vapor atmosphere, wheresaturated with water vapor in a temperature range of 400 to 700° C.Although the pyrolysis processing time is not limited at this time, itis preferably in a range of about 10 to 15 minutes.

In addition, in the case that the oxide film 2 is formed, performing ofa pyrolysis reaction in the atmosphere containing water vapor thereincauses the residual chlorine to be removed and concurrently the layer ofthe oxide film 2 to be unified and further a fine oxide layer to beattained. That is, it is possible to form the layer of the oxide film 2composed of oxide layer of fine crystalline structure showing a quitehigh corrosion resistance characteristic in both oxidizing and reducingatmosphere at the inner surface of the vessel main body 1.

In addition, in the case that the oxide film 2 is formed, it is desiredthat a thickness (nm) of the film under a pyrolysis reaction is about100 to 300 as an amount of one time coating of the coating solution andfurther this is repeated from several times to ten times or so, or asrequired further this is repeated by several times and it is preferablethat the oxide film 2 having a predetermined film thickness (nm) isformed.

A reason why this is formed consists in the fact that when a filmthickness per one time is made thick, it may generate a problem that thefine oxide film 2 is hardly formed and a porous surface is easilyattained. In addition, since it can be considered that volatilesubstance is replaced with oxygen while being volatized under pyrolysisreaction processing and becomes oxide and the oxide film 2 is easilymade porous due to these volatile substances, resulting in that theaforesaid coating→drying→pyrolysis reaction operation are repeated toenable the oxide film 2 composed of fine oxide layer of fine crystallinestructure having a quite high corrosion resistance characteristic inboth oxidizing and reducing atmosphere to be formed at the inner surfaceof the vessel main body 1.

Further, in the case that salt not containing any Cl component at all isapplied as a raw material, the pyrolysis processing is not carried outin atmosphere containing water vapor, but carried out in air atmosphere.However, it is desirable to perform it in the atmosphere containingwater vapor in order to form the oxide film 2 composed of fine oxidelayer as described above at the inner surface of the vessel main body 1.

The oxide film 2 formed at the inner surface of the vessel main body 1in this way is comprised of an oxide layer having fine crystallinestructure that has a quite high corrosion resistance characteristic inboth oxidizing and reducing atmosphere and further the oxide film 2 iscomprised of these assemblies. Then, a slight number of through-passholes are scattered and left at the oxide film 2 formed by the aforesaidpyrolysis reaction processing and the presence of these through-passholes may prevent the oxide film 2 from being broken caused by adifference in thermal expansion (a difference in elongation or shrinkagebetween the vessel and the film) accompanied by rapid increasing ordecreasing of the vessel main body 1 and further prevent the film frombeing peeled off.

Accordingly, in the present invention, it is important that the oxidefilm 2 having some through-pass holes scattered therein is formed(produced).

It is satisfactory that a selection of material about platinum groupmetals forming the oxide film 2 is determined in response to a conditionunder supercritical state. If it is high, Ir is preferable and it isdesirable to apply complex material containing Ta of about 20 to 50 at %as stabilizing agent against Ir in particular. With such an arrangementas above, the oxide film 2 becomes more dense.

Further, as to Ru, since a crystallization temperature of the oxide islow, its forming (production) is easily attained. However, Cl componentis easily left in it, a certain care is required when it is practicallyused.

EXAMPLE 1

A vertical cylindrical vessel type reaction vessel (its volume is 100ml) made of Ni alloy was used and the oxide film 2 with an apparent filmthickness of 3000 nm composed of Ir—20 to 50 at % Ta was formed at theinner surface thereof through thin film formation process divided intoseveral times in operation (coating→drying→pyrolysis→reactionoperation).

In this case, as Ir raw material, Ir chloride IrCl₃ was used and as Taraw material, butyltantalate (Ta (C₃H₇O)₅) was used. Ir chloride wasdissolved in amyl alcohol, put into a heating and distillation equipmentprovided with a circulator and its circulation flow was continued forten hours at a temperature of 90° C. With this processing, a part of Clcomponent of Ir chloride was replaced with amyl alcohol and the Clcomponent of about ¾ was removed. Butyltantalate was added to this Irraw material liquid to produce coating solution for the oxide film 2.

In addition, after the inner surface of the reaction vessel wasdegreased with aceton (cleaning solution), the processing was carriedout for 1 hour in the flow of water vapor of 700° C. to generate Nioxide at the inner surface of the reaction vessel. Then, coatingsolution was applied to the inner surface of this Ni oxide andautomatically dried at a room temperature (approximately 25° C.),thereafter it was forcedly dried at 110° C. and further the pyrolysisreaction processing was carried out for 10 minutes in atmospherecontaining water vapor of 700° C. This coating→drying→pyrolysis reactionoperation was repeated by ten times to form the oxide film 2 with anapparent film thickness of 3000 nm at the inner surface of the vesselmain body 1.

A surface state of the oxide film 2 having a composition range of Ir—20to 50 at % Ta formed at the inner surface of the vessel main body 1 wasobserved with a practical microscope. In addition, a flat plate-likespecies made concurrently at this time (a test piece thickness: 1 mm)was checked for a crystalline phase of the oxide film 2 by an X-raydiffraction method.

Further, a durability test of heating and quenching was carried out in atemperature range from a room temperature (approximately 25° C.) to 650°C. Each of the temperature increasing (heating) time and temperaturedecreasing (quenching) time was set to 3 minutes, respectively.

Under an assumption of processing decomposed produced materials such asPCB or dioxine and the like, a corrosion resistance test was carried outin which pure water containing hydrochloric acid (HCl) of 1000 pmm wasput and held for 10 hours under a supercritical state with a criticaltemperature of 650° C. and a critical pressure of 25 MPa. Then, as anexample of comparison, a similar corrosion resistance test was carriedout under application of the vessel type reaction vessel (usual product)made of Ni having no oxide film formed therein. The result of this testis indicated in Table 1.

TABLE 1 Item 1 2 3 4 5 6 7 8 Material Ir 90 80 70 60 50 40 20 10composition (at %) Ta 10 20 30 40 50 60 80 90 Film crystalline phaseRutile Rutile Rutile Rutile Rutile Rutile Rutile Rutile IrO₂ IrO₂ Ta₂O₅Ta₂O₅ Ta₂O₅ Surface state Slight Smooth Smooth Smooth Smooth SlightSlight Slight crack porous porous porous Heating and No peeling Nopeeling No peeling No peeling No peeling No peeling No peeling Nopeeling cooling test Corrosion resistance Slight No No No No SlightSlight Slight test (immersed in corrosion corrosion corrosion corrosioncorrosion corrosion corrosion corrosion HCI)

As apparent from Table 1, a smooth surface having no cracks at all wasconfirmed even in a composition range of Ir−20 to 50 at % Ta. It wasfound that the crystalline layer was of rutile type and its crystallitesize was 100 nm. Further, even if the heating and cooling were repeated,no peeling was confirmed at all to the oxide film 2.

In addition, the corrosion resistance test also showed that variationsuch as corrosion or the like was not found at all at the reactionvessel of the present invention formed with the oxide film 2. In turn,it was confirmed that the reaction vessel of the prior art applied inthe example of comparison was remarkably corroded.

Further, the reaction vessel of the present invention covered andprotected by the oxide film 2 was applied, air was used as reaction gas,aqueous solution containing PCB of 5000 ppm was used as processingliquid and PCB was oxidized and decomposed under a supercritical statewith a critical temperature of 650° C. and a critical pressure of 25MPa, resulting in that it was confirmed that PCB was oxidized anddecomposed substantially in a complete state and made non-polluted. Atthis time, corrosion at the reaction vessel was not found at all,peeling-off of the oxide film 2 was not found at all either, resultingin that it was confirmed that its durability was remarkably improved andincreased.

EXAMPLE 2

A reaction vessel similar to that described in detail in the example 1was used, and the oxide film 2 with an apparent film thickness of 2500nm composed of Ru−30 to 70 at % Ti was formed at the inner surfacethereof through thin film formation process divided into several timesin operation (coating→drying→pyrolysis reaction operation).

In this case, after the inner surface of the reaction vessel wasdegreased with aceton (cleaning solution), isopropyl alcohol solution ofRh chloride was applied as coating solution to the inner surface, thecoating solution was applied by a brush and automatically dried at aroom temperature (approximately 25° C.), thereafter moisture and freechlorine were dispersed at 180° C. Then, the pyrolysis reactionprocessing was carried out for 10 minutes in atmosphere containing watervapor of 650° C. This coating→drying→pyrolysis reaction operation wasrepeated by ten times to form the oxide film 2 with an apparent filmthickness of 2500 nm at the inner surface of the vessel main body 1.

A surface state of the oxide film 2 having a composition range of Ru−30to 70 at % Ti formed at the inner surface of the vessel main body 1 inthis way was observed with a practical microscope. In addition, a flatplate-like species made concurrently at this time (a test piecethickness: 1 nm) was checked for a crystalline phase of the oxide film 2through X-ray deffraction method.

Further, in order to check durability (film peeling-off or the like) ofthe oxide film 2, a heating and quenching test was carried out in arange of a room temperature (approximately 25° C.) to 650° C. Each ofthe temperature increasing (heating) time and temperature decreasing(quenching) time was set to 3 minutes, respectively.

Under an assumption of processing decomposed produced materials such asPCB or dioxine and the like, a high temperature corrosion resistancetest was carried out for the oxide film 2 in which pure water containinghydrochloric acid (HCl) of 1000 ppm was put and held for 10 hours undera supercritical state with a critical temperature of 650° C. and acritical pressure of 25 MPa. Then, as an example of comparison, asimilar corrosion resistance test was carried out under application ofthe vessel type reaction vessel made of Ni having no oxide film formedtherein. The result of this test is indicated in Table 2.

TABLE 2 Item 1 2 3 4 5 6 7 8 Material Ru 80 70 60 50 40 30 20 10composition (at %) Ti 20 30 40 50 60 70 80 90 Film crystalline phaseRutile Rutile Rutile Rutile Rutile Rutile Rutile Rutile RuO₂ RuO₂anatase anatase Surface state Slight Smooth Smooth Smooth Smooth SmoothSlight Slight crack porous porous Heating and No peeling No peeling Nopeeling No peeling No peeling No peeling No peeling No peeling coolingtest Corrosion resistance Slight No No No No No No Slight test (immersedin corrosion corrosion corrosion corrosion corrosion corrosion corrosioncorrosion HCI)

As apparent from Table 2, a smooth surface having no cracks at all wasconfirmed even in a composition range of Ru−30 to 70 at % Ti. It wasfound that the crystalline phase was of rutile type and stable, and itscrystallite size was 100 nm. Further, even if the heating and coolingwere repeated, no peeling was confirmed at all at the oxide film 2.

In addition, the corrosion resistance test also showed that variationsuch as corrosion or the like was not found at all at the reactionvessel of the present invention formed with the oxide film 2. In turn,it was confirmed that the reaction vessel of the prior art applied inthe example of comparison was remarkably corroded similar to thatdescribed in the example 1.

EXAMPLE 3

A reaction vessel similar to that described in detail in the example 1was used, and the oxide film 2 with an apparent film thickness of 3000nm composed of Rh with 20 to 80 at % Ru and with Ti astetrabutyltitanate added in the same amount (at %) as that of Ru wasformed at the inner surface thereof through thin film formation processdivided into several times in operation (coating→drying→pyrolysisreaction operation).

In this case, the processing was carried out in flow of water vapor of700° C. in the same manner as that described in detail in reference tothe example 1 and the inner surface of the reaction vessel was formedwith Ni oxide by pyrolysis. Then, the aforesaid coating solution wasapplied to the inner surface of the Ni oxide and automatically dried ata room temperature (approximately 25° C.), thereafter it was forcedlydried at 110° C. Then, the pyrolysis reaction processing was carried outfor 10 minutes in atmosphere containing water vapor of 600° C. mixedwith water vapor by 30%. This coating→drying→pyrolysis reactionoperation was repeated by ten times to form the oxide film 2 with anapparent film thickness of 3000 nm at the inner surface of the reactionvessel.

The oxide film 2 having a composition range of Rh−20 to 80 at % Ruformed at the inner surface of the vessel main body 1 in this way had arutile type crystalline layer and Cl component was hardly detected.

In addition, even if the materials such as PCB, dioxine and the like hadcorrosion resistance, it was confirmed that the reaction vessel had astable corrosion resistance in the same manner as that of the preferredembodiments 1 and 2 and its lifetime was also ten times or more ascompared with that of the reaction vessel of the example of comparisonwhere no oxide film was formed.

Since the reaction vessel of the oxidizing and decomposing processingequipment with supercritical water and the method of manufacturing thereaction vessel in accordance with the present invention are constitutedas described above, they have the following actions and effects.

(1) The reaction vessel, showing the largest consumption at theoxidizing and decomposing processing equipment with supercritical water,contains platinum group metal oxide having fine crystalline structurewith a quite high corrosion resistance in both oxidizing and reducingatmosphere formed at its surface. For example, this is covered andprotected by the oxide film composed of Ir-Ta composite oxidescontaining Ta of 20-50 at %, or Ru-Ti composite oxides containing Ti of30-70 at %, so that no corrosion occur even in the atmosphere with thecritical temperature and critical pressure under the condition ofsupercritical water, peeling-off caused by a difference in thermalexpansion due to rapid increasing or decreasing in temperature is notproduced and it is quite stable and a high reliability against thecontinuous use of long period of time can be attained.

(2) Coating solution composed of salt solution is applied to coat thesurface of the reaction vessel formed with the oxide layer for enforcinga bonding with the oxide film through degreasing and surface heatingtreatment, the reaction vessel is processed with pyrolysis reactionprocessing in the atmosphere containing water vapor, thereby the oxidefilm is formed at its surface, so that the bonding with the reactionvessel is more effectively improved. With such an arrangement as above,the bonding (bonding ability) of the oxide film against the reactionvessel is more effectively enforced and the reaction vessel having ahigh reliability with its durability being remarkably improved can bemanufactured.

Accordingly, in accordance with the present invention, it provides thereaction vessel used in the equipment for oxidizing and decomposing withsupercritical water and the method of manufacturing the reaction vesselin which corrosion resistance and durability are remarkably improved ascompared with that of the prior art reaction vessel, the running costaccompanied by replacement or repairing or the like is substantiallydecreased, its continuous application can be carried out for a longperiod of time and it has a high practical effect.

Having described specific preferred embodiments of the invention withreference to the accompanying drawings, it will be appreciated that thepresent invention is not limited to those precise embodiments, and thatvarious changes and modifications can be effected therein by one ofordinary skill in the art without departing from the scope of theinvention as defined by the appended claims.

1. A method of manufacturing a reaction vessel suitable for oxidationand decomposition processing equipment for use with supercritical water,said method comprising the steps of applying a salt solution comprisinga platinum group metal to a surface of said vessel; heating said vesselunder an atmosphere comprising water vapor, thereby forming a filmcomprising an oxide of said platinum group metal on said surface of saidvessel, said film comprising a fine crystalline structure.
 2. The methodof claim 1, further comprising the step of degreasing said surface ofsaid vessel prior to the step of heating said vessel.
 3. The method ofclaim 1, wherein said film comprises Ir oxide, and from 20% to 50% of ametal selected from the group consisting of Ti and Ta.
 4. The method ofclaim 3, wherein said metal is Ta.
 5. The method of claim 1, whereinsaid film comprises Ru oxide, and from 30% to 70% of a metal selectedfrom the group consisting of Ti or Ta.
 6. The method of claim 5, whereinsaid metal is Ti.
 7. The method of claim 1, wherein said salt solutioncomprises a chloride of a platinum group metal.
 8. The method of claim7, wherein said salt solution comprises a chloride of a platinum groupmetal selected from the group consisting of Ir, Ru or Rh.
 9. The methodof claim 1, wherein said salt solution comprises an alkoxide of aplatinum group metal.
 10. The method of claim 9, wherein said saltsolution comprises an alkoxide of a platinum group metal and at leastone other metal selected from the group consisting of Ti or Ta.
 11. Amethod of manufacturing a reaction vessel made of a Ni-base alloysuitable for oxidation and decomposition processing equipment for usewith supercritical water, comprising; (a) applying a solution containinga salt of an Ir, Ru and/or Rh noble metal and a Ti or Ta salt to theinner surface of the vessel to form a coating covering the surface; and(b) pyrolyzing the coating in a water vapor-containing atmosphere toform an anti-corrosive oxide film covering the surface, the filmcomprising (i) in the case of an Ir-Ta composite oxide film from 20 to50 atom % Ta, and (ii) in the case of an Ru-Ti composite oxide film from30 to 70 atom % Ti.
 12. The method of claim 11, further comprising thestep of initially degreasing the inner surface of the vessel.
 13. Themethod of claim 11, wherein the solution comprises a chloride of theplatinum group metal.
 14. The method of claim 11, wherein the solutioncomprises an alkoxide of the platinum group metal.
 15. The method ofclaim 11, wherein the pyrolysis step is carried out in air attemperatures in the range of about 500 to 700° C.
 16. The method ofclaim 11, wherein the pyrolysis is carried out in either oxidizing orreducing atmospheres saturated with water vapor in the range of 400 to700° C. to form a uniform, fine crystalline oxide film.